From: Reto Schuettel <reto-ruby-talk@...>
Date: 2006-03-24T03:30:00+09:00
Subject: Re: drb over pipes

Hi Jonathan

On Thu, Mar 23, 2006 at 12:34:31PM +0000, Jonathan Paisley wrote:
> I implemented a quick hack to do this. Hopefully the code below will help.
> It's a bit of a mess, but allows you to use a DRb scheme like
> 'drbfd://0,1' which means uses file descriptors 0 and 1 (stdin/stdout) for
> communication.
> 
> module DRb

That's great! exactly what I needed. 

For the record: My statement in the first mail wasn't completely
correct, the pipe I used in my example is only a 'one-way' thing. But
ssh actually transports three streams/pipes: stdin, stdout and stderr, so this
isn't really a problem. 

There's one small problem with your fdsocket, it seems like the drb
server/thread doesn't always terminate itself when the streams get
closed. But I will try to investigate this by myself tomorrow :).

I've appended an example which uses your library. It creates two pipes,
forks, connects the pipes to the stdin/stdout of the child and then execs
the ssh client. The same technique could also be used to communicate
with a child (instead of a unix/tcp socket or a simple plain pipe). IMHO
that's really nice, great work Jonathan!

require 'drb'
require 'fdsocket'

ctprd, ctpwr = IO.pipe
ptcrd, ptcwr = IO.pipe

pid = fork 

unless pid
  # child
  ctprd.close
  ptcwr.close

  $stdin.reopen( ptcrd )
  $stdout.reopen( ctpwr )

  exec("ssh", "hostname", "./agent.rb")

  exit # child shounld't reach this point
end

# parent
ctpwr.close
ptcrd.close

fd_read =  ctprd.fileno 
fd_write = ptcwr.fileno

# The URI to connect to
SERVER_URI="drbfd://#{fd_read},#{fd_write}"
DRb.start_service

obj = DRbObject.new_with_uri(SERVER_URI)

[...]


Regards,
Reto Schuettel